1. Field of the Invention
The present invention generally relates to a method and an apparatus for supplying electric components (e.g., electronic components) and an apparatus for mounting electric components, and particularly to the art of improving the efficiency of supplying of electric components.
2. Related Art Statement
U.S. Pat. No. 5,695,309 discloses an electric-component ("EC") supplying apparatus including a plurality of EC supplying units each of which feeds a carrier tape carrying a plurality of electric components ("ECs") and thereby supplies the ECs, one by one, and each one of which is selectively positioned at an EC-supply position to supply one or more ECs. The carrier tape carries the ECs at a predetermined EC-carry pitch and, when a driven member of each EC supplying unit is driven, the carrier tape is fed at a predetermined tape-feed pitch by a carrier-tape feeding device of the unit, so that the ECs are positioned, one by one, at an EC-supply portion of the unit. The plurality of EC supplying units are provided on a movable table such that the respective EC-supply portions of the units are arranged along a straight line, and the movable table is movable in a direction parallel to the straight line, so that each one of the units is selectively positioned at the EC-supply position. A drive member which drives the driven member of each EC supplying unit is provided in the vicinity of the EC-supply position. The plurality of EC supplying units share the drive member and a drive device which drives the drive member. The present EC supplying apparatus can supply the carrier tapes at a lower cost than an apparatus wherein a plurality of EC supplying units include respective drive members and drive devices.
In the above-indicated EC supplying apparatus, the moving of the EC supplying units occurs at a timing different from that at which the feeding of the carrier tape on each EC supplying unit does. For example, after the movable table is moved and the EC-supply portion of one of the EC supplying units is positioned at the EC-supply position, one EC is taken from the carrier tape supplied by the one EC supplying unit, and the drive member is engaged with the driven member of the one unit to feed the carrier tape. After the feeding of the carrier tape, the movable table is moved so that the EC-supply portion of another EC supplying unit is positioned at the EC-supply position.
However, recently, there has been a demand to shorten a positioning time which is needed to position the EC-supply portion of each EC supplying unit at the EC-supply position. For example, the EC supplying apparatus may be employed in an EC mounting system to supply ECs to an EC mounting apparatus of the system. The EC mounting apparatus includes an intermittent-rotation body which intermittently rotates about a vertical axis line at a predetermined rotation-angle pitch, and a plurality of EC holders which is provided on the rotation body such that the EC holders are equiangularly spaced from each other about the vertical axis line at a predetermined spacing-angle pitch equal to the rotation-angle pitch. As the rotation body is intermittently rotated, the EC holders are sequentially moved to each of stop positions including an EC-receive position where each of the EC holders receives an EC from the EC supplying apparatus, and an EC-mount position where each EC holder mounts the EC on a circuit substrate as an example of an object on which ECs are to be mounted. In this case, a cyclic operation time is defined as a time duration needed for an EC holder following another EC holder to reach a stop position after that another EC holder reaches that stop position. Japanese Patent Application laid open for public inspection under Publication No. 6(1994)-342998 discloses an EC mounting apparatus wherein the moving of EC holders by the rotation of an intermittent-rotation body occurs partially concurrently with the EC taking and mounting actions of each of the EC holders, so as to shorten the cyclic operation time of the apparatus. To this end, it is required that the EC-supply portion of each of the EC supplying units be moved to the EC-supply position at a shorter time interval. Accordingly, both a time duration which can be used to position the EC-supply portion of each EC supplying unit at the EC-supply position, and a time duration which can be used to feed the carrier tape on each EC supplying unit are shortened. However, in the case where the acceleration and deceleration of movement of the movable table is increased to shorten the positioning time, the vibration which is produced when the movement of the movable table is started and stopped is increased, which leads to lowering the accuracy of positioning of the EC-supply portion of each EC supplying unit at the EC-supply position. On the other hand, in the case where the acceleration and deceleration of feeding of the carrier tape is increased to shorten the time duration needed to feed the carrier tape, the life expectancy of each EC supplying unit is reduced because the inertia of the unit is great and a great load is applied to the constituent members of the unit (e.g., the members of the carrier-tape feeding device).
In the case where the moving of the EC supplying units and the feeding of each carrier tape are concurrently carried out, the time interval at which the EC-supply portion of each EC supplying unit reaches the EC-supply position can be shortened without having to shorten the time duration needed to position the EC-supply portion of each EC supplying unit at the EC-supply position or the time duration needed to feed the carrier tape.